By taking antiretroviral drugs during pregnancy, this Tanzanian mother lowered the risk of passing HIV to her daughter. Siegfried Modola/AFP/Getty Images hide caption

itoggle caption Siegfried Modola/AFP/Getty Images

Twins in Malawi helped scientists discover a role the gut microbiome appears to play in severe malnutrition. Photograph courtesy of Tanya Yatsunenko hide caption

itoggle caption Photograph courtesy of Tanya Yatsunenko